Determine which wall you want to hang the poster on. Since the poster is large, you will want to put it on a wall that does not have an abundance of clutter around it. Also, you may want to put it on a wall that does not already have other pictures or small posters on it. Hanging your poster on an empty wall will make it more noticeable.
Mark a small line on the wall that is slightly above your eye level. Most people will stand from farther away to view a large poster than they will to view a small poster. Putting the large poster slightly above eye level makes it easier for people to admire the poster from a distance.
Measure the length and width of the large poster. For example, you may measure the poster to be 18 inches long and 13 inches wide. Knowing how long and wide the poster is will help you put it up evenly.
Extend the small line you drew on the wall to match the entire length of the poster. For example, if the poster is 18 inches long, then use a ruler to draw an 18-inch line in pencil.
Draw two small lines in pencil that mark the width of the poster. For example, if the poster is 13 inches wide, measure 13 inches down from the end of either side of the 18-inch line and draw a small pencil mark on the wall.
Put a piece of poster putty at both ends of the 18-inch line, at each of the small pencil marks that define the width of the poster and at the center of the outline. For large posters, poster putty can help to hold it in place more firmly than tape. You can also use both tape and poster putty.
Line up the poster with the pencil markings and press it into the wall. Stand at the back of the room and make sure the poster looks even.